Field
In the area of mobile telecommunications, the performance of single radio voice call continuity (SRVCC) can be enhanced so as to provide video single radio voice call continuity (vSRVCC). Particularly, SRVCC/vSRVCC procedures can be configured for more efficient use of radio resources.
Description of Related Art
The third generation partnership project (3GPP) release eight (rel 8) and later describes a network. The network aims to support universal mobile telecommunication system (UMTS) terrestrial access network (UTRAN), evolved UTRAN (E-UTRAN), and GERAN. 3GPP technical specification (TS) 23.216 specifies SRVCC, which enables voice call to be handed from E-UTRAN/UTRAN packet switched (PS) access to UTRAN/GERAN or 3GPP2 1×CS circuit switched (CS) access. At the edge of E-UTRAN/UTRAN high speed packet access (HSPA) networks, internet protocol (IP) multimedia subsystem (IMS) controlled voice calls can be handed to a circuit switched (CS) network that presently has wider coverage.
Video call continuity from IMS over E-UTRAN access to UTRAN access for calls that are anchored in IMS is also being specified in 3GPP. The definition of SRVCC above is enhanced to mean the process of continuing a voice (or video) call as a user moves from IMS over E-UTRAN access to UTRAN access. The usage of the term SRVCC in 3GPP specifications will keep its original meaning, i.e. voice call continuity, and the term vSRVCC is introduced for single radio video call continuity to differentiate it from single radio voice call continuity (SRVCC).
SRVCC/VSRVCC procedures become more complicated if a user equipment (UE) has multiple simultaneous IMS sessions in active mode.